[N8N-4265] Improve docker compose setup with postgres (#3369)

* persist postgres data using docker volumes

* persist n8n data using docker volumes instead of writing to the host filesystem

* wait for postgres to be actually ready before starting the server

* run web server and workers as separate containers

* create a new `withPostgresAndWorker` example

docker/compose/withPostgresAndWorker/.env

@@ -0,0 +1,9 @@
+POSTGRES_USER=changeUser
+POSTGRES_PASSWORD=changePassword
+POSTGRES_DB=n8n
+
+POSTGRES_NON_ROOT_USER=changeUser
+POSTGRES_NON_ROOT_PASSWORD=changePassword
+
+N8N_BASIC_AUTH_USER=changeUser
+N8N_BASIC_AUTH_PASSWORD=changePassword